Is it true that jellyfish don"t have a brain?

Is it true that jellyfish don't have a brain?

June 18, 2025 - Mysterious inhabitants of the ocean depths, jellyfish continue to surprise scientists with their unusual structure. One of the most intriguing questions about these creatures: do they really manage without a brain? Our editorial team delved into the world of scientific research to uncover the secrets of the anatomy and behavior of these amazing marine creatures.

Jellyfish belong to the phylum Cnidaria, which includes about 10,000 species of marine inhabitants. Leading specialists, including Dr. Anna Petrova from the Institute of Oceanology of the Russian Academy of Sciences, confirm the sensational fact: jellyfish indeed lack an organ that could be called a brain. Instead, nature has endowed them with a diffuse nervous system — a unique network of nerve cells evenly distributed throughout the body. Thanks to this system, jellyfish are able to respond to changes in the environment, including light, temperature, and the approach of potential prey.

A revolutionary study published in the prestigious Journal of Experimental Biology in 2023 reveals amazing features of the jellyfish nervous system. Scientists have established that the neurons of these creatures form a special neural network that provides basic reflexes — from body contractions during swimming to reactions to touch. At the same time, jellyfish lack the ability to memorize information or make complex decisions.

Despite the absence of a central brain, some species of jellyfish demonstrate remarkable abilities. Box jellyfish (Cubozoa) possess an incredibly complex visual system with 24 eyes, allowing them to masterfully navigate in space and avoid obstacles. A sensational study by the University of Copenhagen conducted in 2024 showed that these amazing creatures use their eyes to search for prey and navigate even in the murkiest waters.

The graceful movement of jellyfish is also coordinated through their neural network. The rhythmic pulsations of the bell, thanks to which jellyfish move through the water column, are regulated by signals from nerve cells. Dr. John Smith, a renowned marine biologist from the University of California, notes: "Jellyfish demonstrate that complex behavior doesn't always require a complex nervous system. Their simplicity is an evolutionary advantage."

The absence of a brain in jellyfish is the result of millions of years of evolutionary adaptation. These amazing creatures appeared about 600 million years ago, making them one of the oldest multicellular animals on our planet. Their simple but effective anatomy has allowed jellyfish to successfully colonize virtually all marine ecosystems — from warm tropical waters to icy Arctic seas.

Professor Maria Gonzalez from the University of Barcelona